In the art of light-sensitive silver halide photographic materials for color, particularly light-sensitive silver halide photographic materials for photographing, they have been desired to be endowed with various requisite characteristics, such as high light sensitivity with good image quality. In general, however, higher sensitivity requires the use of silver halide grains having larger grain size, and hence attempts to raise sensitivity have inevitably encountered the problems of increased graininess. Therefore techniques for improving graininess while maintaining high sensitivity have been strongly desired.
One technique used in multi-layer color light-sensitive materials, particularly those where wide latitude for exposure is desired, is to divide a light-sensitive silver halide emulsion layer having light sensitivity to the same spectral wavelength region into plural layers, for example, 2 to 3 layers with different sensitivities. Each layer may be comprised of a silver halide emulsion of a particular size distribution, or multiple grain sizes may be used. Use of multiple layers also allows image quality to be more optimized in certain regions of exposure, such as in areas of low exposure where the highest sensitivity emulsions are used, or in areas of mid- to high-exposure, where less sensitive emulsions may be used.
Color negative films are a class of photosensitive materials that map the luminance (neutral) and chrominance (color) information of a scene to complementary tonal and hue polarities in the negative film. Light areas of the scene are recorded as dark areas on the color negative film, and dark areas of the scene are recorded as light areas on the color negative film. Colored areas of the scene are recorded as complementary colors in the color negative film: red is recorded as cyan, green is recorded as magenta, blue is recorded as yellow, etc. In order to render an accurate reproduction of a scene, a subsequent process is necessary to reverse the luminance and chrominance information back to those of the original scene. One such subsequent process is to optically print the color negative film onto another photosensitive material, such as a color print film or paper.
Photographers and cinematographers desire the noise level in their images to be as low as possible. To minimize image noise in color negative films, it is generally desirable to use the slowest, finest grain stocks that lighting conditions permit. Unfortunately, in many circumstances lighting conditions cannot be altered, either because of the subject material or location constraints. In such instances, the photographer or cinematographer has no choice but to use the most sensitive, albeit the noisiest, stocks available. Medium and high speed color negative stocks are often used in these applications. Film speeds of ISO and El 200 and greater, e.g., are preferred for applications containing critical shadow detail or otherwise for low light conditions.
One can always use larger size emulsions in the fastest layer, or layer with the highest sensitivity, to increase the sensitivity of a film to light, but this generally increases the graininess of the image across the entire range of exposure. This is particularly true where emulsions with the same sensitivity (or speed) to grain efficiency are used. Increasing grain size generally results in speed and granularity increases in a predictable relationship up to a maximum speed. Reports of these observations are illustrated by Farnell, "The Relationship Between Speed and Grain Size", The Journal of Photographic Science, Vol. 17, 1969, pp. 116-125, and Tani, "Factors Influencing Photographic Sensitivity", Journal of Photographic Science and Technology, Japan, Vol. 43, No. 6, 1980 (FIG. 1). For emulsions differing in average grain size below that size which produces maximum speed, the "predictable relationship" referred to above is this: each stop (0.3 log E, where E is exposure in lux-seconds) increase in speed is typically accompanied by a granularity increase of 7 grain units for emulsions in a series being compared which exhibit equal photographic efficiency. For example, assigning a relative log speed of 100 to a reference emulsion, when an emulsion of larger average grain size exhibits a relative log speed of 130 (each unit difference in log speed=0.01 log E) and exhibits a granularity that is increased by 7 grain units, the two emulsions are exhibiting the relationship in performance that the art has established to exist between emulsions of the same photographic efficiency.
For the above reasons, it would be desirable to provide a color photographic light-sensitive material which is excellent in graininess and high in sensitivity. It would be particularly desirable to provide such a film having an ISO or EI speed rating of 200 or higher.